1. Field of the Invention
This invention relates to snow skis for fixed landing gear aircraft.
More particularly, this invention relates to skis for aircraft as described above that are readily attached to and removed from the landing gear of an aircraft.
Still more particularly, this invention relates to skis for aircraft as described above wherein the wheel of the aircraft landing gear projects through the ski enabling the aircraft to land on and take off from paved runways as well as snow and ice landing strips.
Skis for aircraft have a long history. Skis or skids were the landing gear of the Wright brother's first aircraft. Skis mounted to the landing gear of aircraft have permitted aircraft to land and take off from surfaces where wheeled landing gear would not serve.
In order to enable aircraft to land on a bare surface, and to land on an ice or snow covered surface, wheel-through skis were developed. Early “wheel-through ski” landing gear involved the raising of the landing gear off of the ground so that the wheel could be passed through a wheel port in the center of the ski. It is an object of this invention to provide a wheel-through ski that can be attached to and removed from the landing gear of an aircraft without raising the wheel of the aircraft.
Prior art skis for aircraft have been of irregular shape and have had mechanisms of attachment and control that created air drag and the potential for collecting ice and becoming a further drag on the aircraft in the air. It is an object of this invention to provide skis for aircraft that have a single hinged fixed position attachment to the landing gear. Further, it is an object of this invention to provide a ski for aircraft wherein the ski has an airfoil longitudinal profile and the ski attachment means is aerodynamically clean to minimize chances of air drag and/or the collecting of ice on the ski-landing-gear assembly adversely affecting the flight characteristics of the aircraft to which it is attached
Light aircraft do not have wheels that can be turned for steering. When taxiing, the aircraft is steered by means of air control surfaces such as the ailerons and rudder and by braking one wheel. Long thin skis tend to “track” in snow and resist turning so that at slow taxiing speeds the aircraft is difficult to turn. It is an object of this invention to provide a ski for aircraft that is proportionately shorter and wider than conventional skis. A length to width ratio of 4:1 or less provides a ski that has a large area of contact with the snow, a large air foil surface and greater ease of turning at slow speeds and the wheel projection through the ski provides a braking means and a pivot to assist in turning.
When skis mounted on fixed landing gear aircraft have irregularities of their shape and/or the shape of their attachment means, the skis tend to “drag” on the aircraft in flight and to adversely affect the flight characteristics of the aircraft. It is an object of this invention to provide a ski for aircraft that does not appreciably affect the performance of the aircraft in the air and which does positively affect the stall speed of the aircraft during landing.
Conventional aircraft skis are structurally similar to snow skis for downhill skiing in that the load of the rider is transferred to a small area of the middle of the ski. The load is then sustained by the stiffness of the ski bearing down on the snow surface over the length of the ski. The stiffness of the ski is achieved by using metal or composites of natural and synthetic materials that are strong, light weight and durable. It is an object of this invention to provide a ski for aircraft that has a relatively thin skin, an airfoil shape and internal air craft structures that transfer the weight of the aircraft over a wide area of the bottom of the ski. To deal with the wear on the contact surface of the ski of this invention, the inventor provides wear strips of high lubricity, and toughness, detachably secured to the bottom of the ski.
Prior art skis are commonly attached to the landing gear of aircraft by modifying or attaching to the axle of the landing gear wheel. A long ski attached to the axle of the aircraft has the potential of imposing twisting loads of significant magnitude transverse to the axle, that the axle is not designed to accommodate. To deal with this potential, that inventor provides his ski with a small transition piece secured directly to the strut of the landing gear and having a pivot member with an axis of rotation parallel to the axis of rotation of the wheel.
Other objects will be made apparent from the following specifications and from the appended drawings and claims.
2. Brief Discussion of the Prior Art
Prior art skis known to the inventor suffer from one or more of the problems disclosed above and for which this invention provides a solution. Similarly the closest prior art known to the inventor possess one or more of the virtues of this invention.
U.S. Pat. No. 2,925,970 to Heaslip and U.S. Pat. No. 2,977,072 to Ditter et al. teach retractable wheel-through skis wherein the ski is wider forward of the wheel than it is rearward of the wheel thereby providing a two sided notch in the ski into which the wheel can be raised and lowered.
U.S. Pat. No. 3,790,109 to Fischer teaches a steel extension bolted to strut of the landing gear to replace the wheel and axle of the aircraft. Fischer also teaches an aerodynamic shape to reduce air drag.
U.S. Pat. No. 5,599,030 to Campbell et al. teaches detachable wear rods for skis.